luguo

We present a short overview of our recent theoretical developments aiming at the description of exotic nuclear phenomena to be reached and studied at the next-generation radioactive beam facilities. Applications to nuclear shell structure and response of nuclei at the limits of their existence, with a special focus on the physics cases of astrophysical importance, are discussed.

The recent extensions of the covariant energy density functional theory with the quasiparticle-vibration coupling (QVC) are reviewed. Formulation of the Quasiparticle Random Phase Approximation (QRPA) in the relativistic framework is discussed. Self-consistent extensions of the relativistic QRPA imply the QVC which is implemented in two-body propagators in the nuclear medium. This provides fragmentation of the QRPA states describing the damping of the vibrational motion.

We present a theoretical analysis of the competition between so-called nuclear Jacobi and Poincar\'e shape transitions in function of spin - at high temperatures. The latter condition implies the method of choice - a realistic version of the nuclear Liquid Drop Model (LDM), here: the Lublin-Strasbourg Drop (LSD) model. We address specifically the fact that the Jacobi and Poincar\'e shape transitions are accompanied by the flattening of total nuclear energy landscape as function of the relevant deformation parameters what enforces large amplitude oscillation modes that need to be taken into account. For that purpose we introduce an approximate form of the collective Schr\"odinger equation whose solutions are used to calculate the most probable deformations associated with both types of transitions and discuss the physical consequences in terms of the associated critical-spin values and transitions themselves.

Author(s): Ish Mukul, A. Roy, P. Sugathan, J. Gehlot, G. Mohanto, N. Madhavan, S. Nath, R. Dubey, I. Mazumdar, D. A. Gothe, Maninder Kaur, A. K. Rhine Kumar, and P. Arumugam

Background: Giant dipole resonance (GDR) has been used as an important tool for studying nuclear properties in hot rotating nuclei. Exclusive measurements using low-energy γ-ray multiplicity filters provide more control over angular momentum selection in such measurements.

Purpose: Study the effect o...

[Phys. Rev. C 88, 024312] Published Fri Aug 16, 2013

Author(s): P. Descouvemont and M. S. Hussein

We propose an extension of the continuum discretized coupled channels (CDCC) method, where the projectile is described by a microscopic cluster model. This microscopic generalization (MCDCC) relies only on nucleon-target interactions, and therefore presents an important predictive power. Core excita...

[Phys. Rev. Lett. 111, 082701] Published Mon Aug 19, 2013

A project of using a target consisting of the mixture of (249-252)Cf isotopes to be bombarded with the 48Ca beam, aimed to synthesize new isotopes of the heaviest known element Z = 118, is under way at the FLNR in Dubna. In the present work excitation functions for all the reactions: 249Cf(48Ca,xn)(297-x)118, 250Cf(48Ca,xn)(298-x)118, 251Cf(48Ca,xn)(299-x)118 and 252Cf(48Ca,xn)(300-x)118 have been calculated in the framework of the fusion-by-diffusion model, assuming fission barriers, ground-state masses and shell effects of the superheavy nuclei predicted by Kowal et al. Energy dependence of the effective cross sections for the synthesis of selected new isotopes: (293)118, (294)118, (295)118 and (296)118 is predicted for the particular isotopic composition of the Cf target prepared for the Dubna experiment.

We report a direct measurement of the Q-value of the neutrinoless double-beta-decay candidate 48Ca at the TITAN Penning-trap mass spectrometer, with the result that Q = 4267.98(32) keV. We measured the masses of both the mother and daughter nuclides, and in the latter case found a 1 keV deviation from the literature value. In addition to the Q-value, we also present results of a new calculation of the neutrinoless double-beta-decay nuclear matrix element of 48Ca. Using diagrammatic many-body perturbation theory to second order to account for physics outside the valence space, we constructed an effective shell-model double-beta-decay operator, which increased the nuclear matrix element by about 75% compared with that produced by the bare operator. The new Q-value and matrix element strengthen the case for a 48Ca double-beta-decay experiment.

Publication date: 1 October 2013
Source:Physics Letters B, Volume 725, Issues 4–5
Author(s): H.J. Ong , I. Tanihata , A. Tamii , T. Myo , K. Ogata , M. Fukuda , K. Hirota , K. Ikeda , D. Ishikawa , T. Kawabata , H. Matsubara , K. Matsuta , M. Mihara , T. Naito , D. Nishimura , Y. Ogawa , H. Okamura , A. Ozawa , D.Y. Pang , H. Sakaguchi , K. Sekiguchi , T. Suzuki , M. Taniguchi , M. Takashina , H. Toki , Y. Yasuda , M. Yosoi , J. Zenihiro
We have measured the ¹⁶O(p, d) reaction using 198-, 295- and 392-MeV proton beams to search for a direct evidence on an effect of the tensor interactions in light nucleus. Differential cross sections of the one-neutron transfer reaction populating the ground states and several low-lying excited states in ¹⁵O were measured. Comparing the ratios of the cross sections for each excited state to the one for the ground state over a wide range of momentum transfer, we found a marked enhancement of the ratio for the positive-parity state(s). The observation is consistent with large components of high-momentum neutrons in the initial ground-state configurations due to the tensor interactions.

Author(s): Wei-Chia Chen, J. Piekarewicz, and M. Centelles

Background: Average energies of nuclear collective modes may be efficiently and accurately computed using a nonrelativistic constrained approach without reliance on a random phase approximation (RPA).

Purpose: To extend the constrained approach to the relativistic domain and to establish its impact o...

[Phys. Rev. C 88, 024319] Published Wed Aug 21, 2013

Author(s): Bing-Nan Lu (吕炳楠), En-Guang Zhao (赵恩广), and Shan-Gui Zhou (周善贵)

Background: The pseudospin symmetry (PSS) has been studied extensively for bound states. Recently, we justified rigorously that the PSS in single-particle resonant states is exactly conserved when the attractive scalar and repulsive vector potentials of the Dirac Hamiltonian have the same magnitude …

[Phys. Rev. C 88, 024323] Published Mon Aug 26, 2013

Extensive efforts have been made experimentally to reach nuclei in the super heavy mass region of Z = 110 and above with suitable choices of projectile and target nuclei. The cross sections for production of these nuclei are seen to be in the range of a few picobarn or less, and pose great experimental challenges. Theoretically, there have been extensive calculations for highly asymmetric (hot-fusion) and moderately asymmetric (cold-fusion) collisions and only a few theoretical studies are available for near symmetric collisions to estimate the cross sections for production of super-heavy nuclei. In the present article, we revisit the symmetric heavy ion reactions with suitable combinations of projectile and target nuclei in the rare-earth region, that will lead to compound systems with very low excitation energy and with better neutron-to-proton ratio for higher stability.

Relativistic corrections to the reaction kinematic parameters were made for elastic scattering of \nuc{6}{Li}, \nuc{12}{C} and \nuc{40}{Ar} from \nuc{40}{Ca}, \nuc{90}{Zr}, and \nuc{208}{Pb} targets at incident energies between 20 and 100 MeV/nucleon. Results of optical model calculations show that the effects of such corrections are important in describing the angular distributions of elastic scattering cross sections for heavy ion scattering at incident energies as low as around 40 MeV/nucleon. The effects on the total reaction cross sections on the other hand, were found to be small within the energy range studied when the optical model potential is fixed.

Author(s): M. Rashdan

The fusion cross sections, barrier, and spin distributions of stable and unstable nuclei are investigated through a coupled-channel approach using a density and energy-dependent effective Brueckner G-matrix interaction. Calculations are carried out for the fusion reactions ^{16,18,20,22,24}O + ⁵⁸Ni and...

[Phys. Rev. C 88, 024615] Published Tue Aug 27, 2013

The strength functions of giant dipole resonance (GDR) in oxygen $^{18 - 24}$O, calcium $^{50 - 60}$Ca, and tin $^{120 - 130}$Sn isotopes are calculated within the phonon damping model under three approximations: without superfluid pairing, including BCS pairing, and exact pairing gaps. The analysis of the numerical results shows that exact pairing decreases the two-neutron separation energy in light nuclei, but increases it in heavy nuclei as compared to that obtained within the BCS theory. In neutron-rich medium and heavy nuclei, exact pairing significantly enhances the strength located at the low-energy tail of the GDR, which is usually associated with the pygmy dipole resonance. The line shape of the GDR changes significantly with increasing the neutron number within an isotopic chain if the model parameter is kept fixed at the value determined for the stable isotope.

Author(s): Lucas O. Wagner, E. M. Stoudenmire, Kieron Burke, and Steven R. White

A sufficiently damped iteration of the Kohn-Sham (KS) equations with the exact functional is proven to always converge to the true ground-state density, regardless of the initial density or the strength of electron correlation, for finite Coulomb systems. We numerically implement the exact functiona...

[Phys. Rev. Lett. 111, 093003] Published Wed Aug 28, 2013

We address the stopping in heavy-ion induced reactions around the Fermi energy using central collisions recorded with \emph{INDRA} $4\pi$ array. The stopping is minimal around the Fermi energy and corresponds to the disappearance of the Mean-Field effects and the appearance of nucleon-nucleon elastic collisions. This phenomenon is attributed to a change in the dissipation regime going from 1-body (Mean-Field) dissipation at low incident energy to 2- body (nucleonic collisions) above the Fermi energy. A connection to the in-medium transport properties of nuclear matter is proposed and comprehensive values of the nucleon mean free path $\lambda_{NN}$ and the nucleon-nucleon cross section are extracted.

Author(s): Ikuko Hamamoto

Applying a relatively simple particle-rotor model to odd-odd nuclei, the possible presence of multi-chiral-pair bands is looked for, where chiral-pair bands are defined not only by near degeneracy of the levels of two bands but also by similar expectation values of squared components of three angula...

[Phys. Rev. C 88, 024327] Published Fri Aug 30, 2013

Author(s): M. Murakami, S. Goto, H. Murayama, T. Kojima, H. Kudo, D. Kaji, K. Morimoto, H. Haba, Y. Kudou, T. Sumita, R. Sakai, A. Yoneda, K. Morita, Y. Kasamatsu, H. Kikunaga, and T. K. Sato

Production cross sections of Rf isotopes in the ²⁴⁸Cm + ¹⁸O reaction were measured at the beam energy range of 88.2 to 101.3 MeV by use of a gas-filled recoil ion separator. The excitation functions of ²⁶⁰Rf, ²⁶¹Rf^a, and ²⁶²Rf were obtained together with those of spontaneously fissioning nuclides wh...

[Phys. Rev. C 88, 024618] Published Fri Aug 30, 2013

Author(s): C. Simenel, R. Keser, A. S. Umar, and V. E. Oberacker

We perform a study of ¹⁶O+¹⁶O fusion at above and below the interaction barrier energies using three-dimensional time-dependent Hartree-Fock (TDHF) calculations at above-barrier energies and density-constrained TDHF calculations for the entire energy range. We discuss the variations of the experimen...

[Phys. Rev. C 88, 024617] Published Fri Aug 30, 2013

The present document focuses on the theoretical foundations of the nuclear energy density functional (EDF) method. As such, it does not aim at reviewing the status of the field, at covering all possible ramifications of the approach or at presenting recent achievements and applications. The objective is to provide a modern account of the nuclear EDF formalism that is at variance with traditional presentations that rely, at one point or another, on a {\it Hamiltonian-based} picture. The latter is not general enough to encompass what the nuclear EDF method represents as of today. Specifically, the traditional Hamiltonian-based picture does not allow one to grasp the difficulties associated with the fact that currently available parametrizations of the energy kernel $E[g',g]$ at play in the method do not derive from a genuine Hamilton operator, would the latter be effective. The method is formulated from the outset through the most general multi-reference, i.e. beyond mean-field, implementation such that the single-reference, i.e. "mean-field", derives as a particular case. As such, a key point of the presentation provided here is to demonstrate that the multi-reference EDF method can indeed be formulated in a {\it mathematically} meaningful fashion even if $E[g',g]$ does {\it not} derive from a genuine Hamilton operator. In particular, the restoration of symmetries can be entirely formulated without making {\it any} reference to a projected state, i.e. within a genuine EDF framework. However, and as is illustrated in the present document, a mathematically meaningful formulation does not guarantee that the formalism is sound from a {\it physical} standpoint. The price at which the latter can be enforced as well in the future is eventually alluded to.

Author(s): Roi Baer, Daniel Neuhauser, and Eran Rabani

We formulate the Kohn-Sham density functional theory (KS-DFT) as a statistical theory in which the electron density is determined from an average of correlated stochastic densities in a trace formula. The key idea is that it is sufficient to converge the total energy per electron to within a predefi...

[Phys. Rev. Lett. 111, 106402] Published Wed Sep 04, 2013

Author(s): Y. F. Niu (牛一斐), Z. M. Niu (牛中明), N. Paar, D. Vretenar, G. H. Wang (王刚华), J. S. Bai (柏劲松), and J. Meng (孟杰)

We formulate the finite-temperature relativistic Hartree-Bogoliubov theory for spherical nuclei based on a point-coupling functional, with the Gogny or separable pairing force. Using the functional PC-PK1, the framework is applied to the study of pairing transitions in Ca, Ni, Sn, and Pb isotopic ch...

[Phys. Rev. C 88, 034308] Published Fri Sep 06, 2013

Author(s): Yukio Hashimoto

A new numerical method of calculating the Hartree-Fock-Bogoliubov (HFB) and time-dependent HFB (TDHFB) with the Gogny interaction is proposed. The three-dimensional harmonic-oscillator (3DHO) basis functions are replaced by one-dimensional spatial grid points of Lagrange mesh plus two-dimensional ha...

[Phys. Rev. C 88, 034307] Published Fri Sep 06, 2013

Publication date: March 2014
Source:Atomic Data and Nuclear Data Tables, Volume 100, Issue 2
Author(s): B. Pfeiffer, K. Venkataramaniah, U. Czok, C. Scheidenberger
Atomic mass reflects the total binding energy of all nucleons in an atomic nucleus. Compilations and evaluations of atomic masses and derived quantities, such as neutron or proton separation energies, are indispensable tools for research and applications. In the last decade, the field has evolved rapidly after the advent of new production and measuring techniques for stable and unstable nuclei resulting in substantial ameliorations concerning the body of data and their precision. Here, we present a compilation of atomic masses comprising the data from the evaluation of 2003 as well as the results of new measurements performed. The relevant literature in refereed journals and reports as far as available, was scanned for the period beginning 2003 up to and including April 2012. Overall, 5750 new data points have been collected. Recommended values for the relative atomic masses have been derived and a comparison with the 2003 Atomic Mass Evaluation has been performed. This work has been carried out in collaboration with and as a contribution to the European Nuclear Structure and Decay Data Network of Evaluations.

The experimental and theoretical studies of Giant Resonances, or more generally of the nuclear collective vibrations, are a well established domain in which sophisticated techniques have been introduced and firm conclusions reached after an effort of several decades. From it, information on the nuclear equation of state can be extracted, albeit not far from usual nuclear densities. In this contribution, which complements other contributions appearing in the current volume, we survey some of the constraints that have been extracted recently concerning the parameters of the nuclear symmetry energy. Isovector modes, in which neutrons and protons are in opposite phase, are a natural source of information and we illustrate the values of symmetry energy around saturation deduced from isovector dipole and isovector quadrupole states. The isotopic dependence of the isoscalar monopole energy has also been suggested to provide a connection to the symmetry energy: relevant theoretical arguments and experimental results are thoroughly discussed. Finally, we consider the case of the charge-exchange spin-dipole excitations in which the sum rule associated with the total strength gives in principle access to the neutron skin and thus, indirectly, to the symmetry energy.

Author(s): M. Kortelainen, J. Erler, W. Nazarewicz, N. Birge, Y. Gao, and E. Olsen

Background: Neutron-skin thickness is an excellent indicator of isovector properties of atomic nuclei. As such, it correlates strongly with observables in finite nuclei that depend on neutron-to-proton imbalance and the nuclear symmetry energy that characterizes the equation of state of neutron-rich...

[Phys. Rev. C 88, 031305] Published Mon Sep 09, 2013

Author(s): Kenichi Yoshida and Takashi Nakatsukasa

Giant multipole resonances in Nd and Sm isotopes are studied by employing the quasiparticle-random-phase approximation on the basis of the Skyrme energy-density-functional method. Deformation effects on giant resonances are investigated in these isotopes, which manifest a typical nuclear shape chang...

[Phys. Rev. C 88, 034309] Published Mon Sep 09, 2013

Author(s): D. Rudolph et al.

A high-resolution α, x-ray, and γ-ray coincidence spectroscopy experiment was conducted at the GSI Helmholtzzentrum für Schwerionenforschung. Thirty correlated α-decay chains were detected following the fusion-evaporation reaction ⁴⁸Ca+²⁴³Am. The observations are consistent with previous assignments...

[Phys. Rev. Lett. 111, 112502] Published Tue Sep 10, 2013

We analyze microscopic many-body calculations of the nuclear symmetry energy and its density dependence. The calculations are performed in the framework of the Brueckner-Hartree-Fock and the Self-Consistent Green's Functions methods. Within Brueckner-Hartree-Fock, the Hellmann-Feynman theorem gives access to the kinetic energy contribution as well as the contributions of the different components of the nucleon-nucleon interaction. The tensor component gives the largest contribution to the symmetry energy. The decomposition of the symmetry energy in a kinetic part and a potential energy part provides physical insight on the correlated nature of the system, indicating that neutron matter is less correlated than symmetric nuclear matter. Within the Self-Consistent Green's Function approach, we compute the momentum distributions and we identify the effects of the high momentum components in the symmetry energy. The results are obtained for the realistic interaction Argonne V18 potential, supplemented by the Urbana IX three-body force in the Brueckner-Hartree-Fock calculations.

Recently a new observable to study halo nuclei was introduced, based on the ratio between breakup and elastic angular cross sections. This new observable is shown by the analysis of specific reactions to be independent of the reaction mechanism and to provide nuclear-structure information of the projectile. Here we explore the details of this ratio method, including the sensitivity to binding energy and angular momentum of the projectile. We also study the reliability of the method with breakup energy. Finally, we provide guidelines and specific examples for experimentalists who wish to apply this method.